Re: Suggestion to add --continue-client-on-abort option to pgbench

> On Nov 13, 2025, at 13:50, Yugo Nagata <nagata@sraoss.co.jp> wrote:
> 
> 
> To trigger a deadlock error, the tables need to have enough rows so that the scan takes some
> time. In my environment, about 1,000 rows were enough to cause a deadlock.
> 

Yes, after inserting 1000 rows, I got the assert triggered. I added some logs to track what had been read:

```
% pgbench -n  --failures-detailed  -M extended -j 2 -c 2  -f deadlock.sql -f deadlock2.sql evantest
pgbench (19devel)
EVAN: on error discard: Got result: res=11, conn=0
EVAN: on error discard: Got result: res=7, conn=0
EVAN: discardUntilSync: Got result: res=10, conn=0 <== received sync
EVAN: discardUntilSync: Got sync, conn=0
EVAN: discardUntilSync: Got result: res=2, conn=0 <== then immediately received result of next select, without a null res in between
EVAN: discardUntilSync: Got result value: 2, conn=0
Assertion failed: (res == ((void*)0)), function discardUntilSync, file pgbench.c, line 3579.
zsh: abort      pgbench -n --failures-detailed -M extended -j 2 -c 2 -f deadlock.sql -f
```

Looks like there is not a null result following the PIPELINE_SYNC message.

So the code comment seems to not accurate:
```
/*
* PGRES_PIPELINE_SYNC must be followed by another
* PGRES_PIPELINE_SYNC or NULL; otherwise, assert failure.
*/
Assert(res == NULL);
```

Then I made a dirty change that return from discardUntilSync() once receives SYNC:
```
		if (PQresultStatus(res) == PGRES_PIPELINE_SYNC)
		{
			printf("EVAN: discardUntilSync: Got sync, conn=%d\n",
				   PQstatus(st->con));
			received_sync = true;
			st->num_syncs = 0;
			PQclear(res);
			break;
		}
```

that eliminates the assert:
```
% pgbench -n  --failures-detailed  -M extended -j 2 -c 2  -f deadlock.sql -f deadlock2.sql evantest
pgbench (19devel)
EVAN: on error discard: Got result: res=11, conn=0
EVAN: on error discard: Got result: res=7, conn=0
EVAN: discardUntilSync: Got result: res=10, conn=0
EVAN: discardUntilSync: Got sync, conn=0
pgbench: error: client 0 aborted: failed to exit pipeline mode for rolling back the failed transaction
transaction type: multiple scripts
scaling factor: 1
query mode: extended
number of clients: 2
number of threads: 2
maximum number of tries: 1
number of transactions per client: 10
number of transactions actually processed: 10/20
number of failed transactions: 0 (0.000%)
number of serialization failures: 0 (0.000%)
number of deadlock failures: 0 (0.000%)
latency average = 203.933 ms
initial connection time = 3.006 ms
tps = 9.807152 (without initial connection time)
SQL script 1: deadlock.sql
 - weight: 1 (targets 50.0% of total)
 - 8 transactions (80.0% of total)
 - number of transactions actually processed: 8 (tps = 7.845722)
 - number of failed transactions: 0 (0.000%)
 - number of serialization failures: 0 (0.000%)
 - number of deadlock failures: 0 (0.000%)
 - latency average = 127.115 ms
 - latency stddev = 332.002 ms
SQL script 2: deadlock2.sql
 - weight: 1 (targets 50.0% of total)
 - 2 transactions (20.0% of total)
 - number of transactions actually processed: 2 (tps = 1.961430)
 - number of failed transactions: 0 (0.000%)
 - number of serialization failures: 0 (0.000%)
 - number of deadlock failures: 0 (0.000%)
 - latency average = 1.347 ms
 - latency stddev = 0.207 ms
pgbench: error: Run was aborted; the above results are incomplete.
```

So, I think now the key problem is to confirm if there must be a NULL following PGRES_PIPELINE_SYNC.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/